The invention relates to improvements in ophthalmologic apparatus in general, and more particularly to improvements in apparatus for optical and photometric examination of patients' eyes. Still more particularly, the invention relates to improvements in ophthalmologic apparatus wherein an illuminating unit furnishes light for a second (viewing) unit which serves to permit an examination of a selected portion (particularly the fundus) of a patient's eye.
Heretofore known ophthalmologic apparatus of the above outlined character exhibit the drawback that, if a patient's eye is to be reexamined once or at certain intervals, the physician in charge cannot repeatedly select one and the same position of the center of curvature of the front surface of the cornea or the optical axis of a patient's eye with reference to the apparatus and/or vice versa. A conventional ophthalmologic apparatus is disclosed, for example, in Swiss Pat. No. 622 261. On the other hand, repeated selection of one and the same position of a patient's eye relative to an ophthalmologic apparatus is not only desirable but necessary if a physician is to successfully compare the results of one or more earlier examinations with those of a subsequent examination. As a rule, the head of a patient is affixed to a conventional support. The patient thereupon focusses the eye to be examined upon a reference mark which is projected into the path of rays passing through a microscope. The apparatus is adjustable in three different directions (along the X, Y and/or Z axis), and the person in charge of the examination shifts the apparatus with reference to the eye in the direction(s) of one or more axes until such person discerns a sharp image of the fundus or another part of the eye which requires examination. As mentioned above, conventional apparatus cannot be readily moved exactly to the same position as during one or more earlier examinations. This causes the development of different reflections of light during successive examinations which, in turn, results in inaccurate measurements of brightness and, due to the lack of reproducibility, the thus obtained measurement values are often totally useless to the physician in charge.